The Salt

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Fri July 11, 2014

Are Organic Vegetables More Nutritious After All?

There may never be an end to arguments over whether organic food is more nutritious. But a new study is the most ambitious attempt so far to resolve the issue — and it concludes that organic fruit and vegetables offer a key benefit.

It's a scientific reply to an analysis that some researchers at Stanford University published two years ago. That paper, which generated lots of media coverage and much controversy, reviewed more than 200 studies of organic and conventional food, and concluded that organic foods do not really offer any significant nutritional benefit.

This new analysis, from a group of scientists mostly based in Europe, crunched data from an even bigger pile of studies: 343 of them, carried out over the past several decades. It will be published Monday in the British Journal of Nutrition.

The new analysis repeats some of the Stanford group's findings. It finds that organic and conventional vegetables offer similar levels of many nutrients, including minerals, vitamin C and vitamin E. Conventional crops are higher in protein. And there are fewer pesticide residues on organic foods, as you'd expect.

But the group found a significant difference in the levels of special compounds called antioxidants. "Across the important antioxidant compounds in fruits and vegetables, organic fruits and vegetables deliver between 20 and 40 percent higher antioxidant activity," says Charles Benbrook, from Washington State University's Center for Sustaining Agriculture and Natural Resources, a co-author of the study.

These antioxidant compounds, which go by names like flavonoids and carotenoids, are getting a lot of attention lately. Their effects remain somewhat murky, but scientists say they can protect cells from the effects of aging, or from the sort of damage that can lead to cancer.

Benbrook says this is a big reason why public health experts want us all to eat more fruits and vegetables: They deliver a good dose of antioxidants. And if organic produce provides more of them, he says, "we think that's a big deal."

Benbrook thinks there are a couple of reasons why they're seeing this result.

First, plants make these compounds to protect themselves when they run into challenges like insects or diseases. And organic crops, because they aren't protected by as many chemical pesticides, have to fight off more hungry bugs. "Plants in an organic field are getting chewed on," he says.

The second reason, Benbrook says, is that organic crops aren't getting as much fertilizer. More heavily fertilized conventional crops may grow faster and get bigger, but as a result, their nutrients may get diluted.

"That's why when you buy these great big juicy apples that are just sweet as sin, it's that extra moisture and carbohydrate that dilutes the vitamin C and the anthocyanins," he says.

This analysis, however, probably isn't the end of this debate.

Jeffrey Blumberg, a professor of nutrition at Tufts University, says attempts to draw conclusions from collections of hundreds of different studies, each one comparing organic and conventional food, are beset by a host of methodological problems. For one thing, there's no single "organic" or "conventional" production system.

Some organic crops get lots of organic fertilizer; some don't. Some are protected with lots of natural pesticides; some are not. Conventional practices vary widely, too. So it's difficult to know, in the end, what you really are comparing. And food that's compared in these studies may not be the same as the food you're buying in the store.

In any case, Blumberg says, the difference in nutritional quality between organic and non-organic fruits and vegetables really isn't that big — especially when you consider the gap between what Americans should eat, and what they really consume.

"Most Americans are getting only a couple of servings of fruits and vegetables every day," he says. "We're recommending that they get up to nine servings."

What really will make a difference in people's health, he says, is just eating more fruits, vegetables and whole grains. If you eat plenty of these foods — whether they're organic or not — you'll get plenty of antioxidants.

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Transcript

MELISSA BLOCK, HOST:

This is ALL THINGS CONSIDERED from NPR News. I'm Melissa Block. There has been a long-running debate over whether organic food is more nutritious. A new study in the British Journal of Nutrition comes to the conclusion that organic food may not be superior across the board, but it does have an advantage when it comes to those valuable compounds antioxidants. NPR's Dan Charles reports.

DAN CHARLES, BYLINE: This new study is a kind of formal reply to another one published two years ago. That paper reviewed a couple of hundred studies of organic and conventional food, and concluded that organic foods don't really offer any significant nutritional benefit. But this new analysis from another group of scientists collected data from an even bigger pile of studies - 343 in all, carried out over the past 20 years. Charles Benbrook, from Washington State University's Center for Sustaining Agriculture and Natural Resources, is one of the co-authors. He says they found that, indeed, in many ways, organic and conventional veggies are not very different. They saw no difference in things like minerals, vitamin C, vitamin E. But there were fewer pesticide residues, as you'd expect, and there was a significant difference in the amount of special compounds called antioxidants.

CHARLES BENBROOK: Across the important antioxidant compounds of fruits and vegetables, organic fruits and vegetables deliver between 20 and 40 percent higher antioxidant activity.

CHARLES: These compounds - they go by names like flavonoids and carotenoids - are getting a lot of attention lately. Scientists say they can protect cells from the effects of aging or from the sort of damage that can lead to cancer. Benbrook says they're a big reason why public health experts want us all to eat more fruits and vegetables. And it looks like you'll get more of them from organic food.

BENBROOK: We think that that's a big deal.

CHARLES: Benbrook thinks there are a couple of reasons why they're seeing this result. First, plants make these compounds to protect themselves when they run into challenges like insects or diseases. And organic crops, because they aren't getting much help from chemical pesticides, have to fight off more hungry bugs.

BENBROOK: Plants in an organic field - they are getting chewed on some.

CHARLES: The second reason, Benbrook says, is that organic crops usually get less fertilizer. Conventional crops may grow faster and get bigger, but it may be that their nutrients get diluted.

BENBROOK: That's why, you know, when you buy these great, big, juicy apples that are just sweet as sin, it's that extra moisture and carbohydrate that dilutes the vitamin C and the anthocyanins.

CHARLES: This latest analysis, though, probably is not going to end the debate over whether organic food is really more nutritious. Jeffrey Blumberg, who's a professor of nutrition at Tufts University, says one big problem is you don't really know what you're comparing. Organic crops are grown under many different conditions. Some get lots of organic fertilizer - some don't. Some are protected with lots of natural pesticides - some aren't. Conventional practices vary widely, too. So the food in these studies may not be the same as the food you're buying in the store. And in any case, he says, the difference in nutritional quality between organic and nonorganic fruits and vegetables is not really that big, especially when you consider what Americans actually are eating.

JEFFREY BLUMBERG: Most Americans are only getting a couple servings of fruits and vegetables every day, whereas we're recommending they get up to nine servings.

CHARLES: That's what really will make a difference in people's health, he says - just eating more fruits and vegetables and whole grains. If you eat plenty of them, whether they're organic or not, you'll get plenty of antioxidants. Dan Charles, NPR News. Transcript provided by NPR, Copyright NPR.